1. Field of the Invention
This invention relates to apparatus for synchronously performing a plurality of operations on a web of stock material and more particularly to a light duty stamping machine in which a plurality of operations are performed on a web of stock material in timed, synchronous relation where a change in the rate of feed of the stock material to a stamping unit results in a change in the rate of operation of the other units to maintain the operation of all the units in timed relation.
2. Description of the Prior Art
It is the conventional practice in high speed automatic press operations to feed a strip of material from a coil to the dies of the press for punching, stamping, cutting or the like of a preselected length of the material from the web of stock material. The material must be fed to the stamping or punching unit in timed relation with the stamping or punching operation so that when the dies contact the material, the material is released from engagement by the feed rolls so that the feed is interrupted and the material is stationary relative to the dies. After the stamping or punching operation is completed, the feed roll unit is actuated to advance another preselected length of material at a preselected feed rate to the press. Therefore, the feeding of the stock material to the press must be coordinated with each operation whether it be stamping, punching, cutting or any other operation so that prior to each operation a new segment of the stock material is in correct register with the operation to be preformed.
In heavy duty stamping and pressing operations, as disclosed in U.S. Pat. No. 3,483,782, it is well known to drivingly connect the feed roll unit to the power punch press crankshaft. Continuous rotation of the crank shaft is converted by an index drive to non-continuous, incremental movement of an output shaft drivingly connected to a driven feed roll of the feed roll unit. With this arrangement the feed roll is not rotated during the stamping or pressing portion of the forming operation. After the punching or stamping operation is completed, the feed roll is rotated to advance another peselected length of stock material from a roll of stock material to the press dies. The feeding of stock material to the press is completed prior to the operation of forming the stock material by stamping, punching, or the like.
U.S. Pat. Nos. 2,272,215; 2,314,367; 2,480,781; 3,053,129; 3,102,673; 3,143,938; 3,244,045; 3,315,553; 3,768,349 and 3,978,703 disclose punching and stamping apparatus in which stock material is unreeled from a coil, stamped or punched, and cut into equal lengths of stamped stock material. The principal factor in feeding the stock material to the punch press in these devices in coordinating the feeding operation with the punching operation and the other operations performed on the stock material subsequent to the punching operation, such as cutting and stacking the final product.
When a plurality of motors for individually powering each of the stock forming devices are utilized considerable difficulty is encountered in synchronizing the feeding operation, for example, with the punching or stamping and cutting operations. When separate drive units are employed, a change in the feed rate necessitates a change in the rate of stamping the stock material and cutting preselected lengths of the stamped stock material from the web. Adjustments in the rate in which the individual operations are performed to maintain the operations synchronized generally requires considerable time and skill of an experienced technician.
U.S. Pat. No. 4,138,913 discloses a common drive for the punching operation and the feeding operation in a heavy duty punch press by drivingly connecting the feed roll unit to the punch press. In addition, a stock pulling unit is drivingly connected to the feed roll unit so that stock material is continuously unreeled from a roll and fed to the feed roll unit. The feed roll unit in timed relation with the cyclical movement of the punch press dies intermittently feeds preselected lengths of the stock material to the punch press. During the punching operation, rotation of the feed roll is interrupted and the stock pulling unit continues to unreel lengths of stock material from the reel. Thus a loop is formed in the stock material between the stock pulling unit and the feed roll unit. At the end of each punching cycle, the material formed in the loop is fed by the feed roll unit to the punch press.
U.S. Pat. Nos. 2,314,367; 2,272,215; 2,480,781 and 3,053,129 also disclose a single drive motor to provide both continuous unreeling from a coil and intermittent feeding to a punch press. In addition, U.S. Pat. No. 3,465,958 discloses a standard Geneva drive coupled to a continuously rotating input shaft for converting the continuous rotary motion of an output shaft to intermittent rotary motion ot effect stepped advancement of cards to be punched with holes. The same continuous drive shaft is coupled by eccentrics to the punches at each punch position whereby a selected punch is oscillated at right angles to the path of movement of the card to achieve penetration during dwell of the feed mechanism.
While it has been suggested by the prior art devices to drivingly connect a stock pulling unit and an intermittent feed unit to the drive of a punch press there is need to provide a stock material forming apparatus that utilizes a single source of power for operating a plurality of stock material forming devices such as a stock pulling unit, a feed roll unit, a stamping or punching unit, a cutting unit, and the like where the rate of operation of any of the units can be varied such as the feed unit and the rates of operation of the other units change automatically so that all the operations performed on the stock material are maintained in timed, synchronous relation.